EP1036299B1

EP1036299B1 - Apparatus and method for blast suppression

Info

Publication number: EP1036299B1
Application number: EP98960975A
Authority: EP
Inventors: John G. Bureaux; George Cowan; Patricia Mountain; Douglas Eaton; Christopher Corbin
Original assignee: Royal Canadian Mounted Police
Current assignee: Royal Canadian Mounted Police
Priority date: 1997-12-12
Filing date: 1998-12-11
Publication date: 2003-08-06
Anticipated expiration: 2018-12-11
Also published as: EP1036299A1; CA2314245C; HK1033353A1; IL136683A; AU1657699A; DE69817015D1; IL136683A0; AU737672B2; CA2314245A1; US6439120B1; WO1999031457A1; DE69817015T2

Description

BACKGROUND OF THE INVENTION

This invention relates to explosive blast suppression, and to an apparatus and method for use therefor.

DESCRIPTION OF THE PRIOR ART

The use of aqueous foam enclosed in various barrier structures has been employed in the prior art with mixed success. Two related relevant references are, U.S. Patents 5,225,622 and 5,394,786. Both references describe a foam-filled enclosure for explosive blast suppression. Figure 10 of the first patent illustrates a dome-shaped enclosure. It is noted that the diameter of the dome and hence the volume of the enclosure is quite large, i.e. of the order of 3.66m (12ft) and is thus inefficient and unnecessarily bulky.

Moreover the foam expansion ratio is quite high i.e. 135-1000:1. This causes instability and early breakdown of the foam. When a blast occurs under aqueous foam, as each bubble bursts, there is an incremental loss of the blast overpressure energy, the net effect of millions of bubbles being destroyed represents a significant blast reduction. Working from the premise that the suppressant quality of the foam would be a function of the mechanical generation and strength of the bubble we have found that superior blast suppression can be achieved by significantly reducing the size of the dome shaped enclosure and the amount of foam material, and by employing a selected aqueous high stability flowable foam material having a low expansion ratio, and low drainage rate properties.

US-A-4392412 describes an hemispherical membrane defined by an upstanding wall; and a positioning means associated with the membrane for positioning the explosive device within the membrane equidistant from any point of the wall, whereby upon detonation of the explosive device so positioned, the blast is suppressed.

US-A-4543872 discloses a blast attenuator employing a foam generating cannister for dispensing foam into a cylinder and an orifice in the centre of a flexible plastic floor is provided so as to insert therethrough an explosive device.

US-A-4589341 also describes a high expansion foam material.

In accordance with a first aspect of the present invention, an apparatus for suppression of a blast from an explosive device comprises:

a) a hemispherical enclosure defined by an upstanding wall, wherein the enclosure is made of a composite textile material, comprising one or more layers of a ballistic fabric material, sandwiched between inner and outer layers of a light-weight rip-stop nylon fabric material,

b) positioning means associated with the enclosure for positioning the explosive device within the enclosure substantially equidistant from any point on the wall,

c) an opening in the wall, and

d) an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, substantially filling the enclosure and covering the explosive device, whereby upon detonation of the explosive device so positioned, the blast is suppressed.

In accordance with a second aspect of the present invention, a method for suppression of a blast from an explosive device comprises:

a) providing a hemispherical enclosure defined by an upstanding wall, wherein the enclosure is made of a composite textile material comprising one or more layers of a ballistic fabric material, sandwiched between outer and inner layers of a waterproof nylon fabric material,

b) positioning the explosive device within the enclosure, substantially equidistant from any point on the wall, and

c) substantially filling the enclosure and covering the device with an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, whereby upon detonation of the device so positioned, the blast is suppressed.

An example of an apparatus and method according to the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a perspective view of a hemispherical enclosure;

Figure 2 is a perspective view of a hemispherical enclosure cut away in part to illustrate the cross-section of the composite material from which it is constructed; and,

Figure 3 is a perspective view of an apparatus according to an example of the invention.

As seen in Figures 1 and 2, the hemispherical enclosure 10 is defined by an upstanding wall, and as having a diameter of 1.5-2.7m (5-9ft). It will be appreciated that other enclosure sizes, particularly smaller sizes, are within the scope of this invention.

Foam injection openings 12 are provided near the top of the enclosure, and a door opening 14 is provided at the base. An optional opening 16 is provided near the base for foam injection, or to remove noxious gases resulting from a low energy device when no foam is used. For such cases a filter/pump device could be used. All of the openings include a sealing flap (Figure 3) and the opening 16 includes a zipper or other suitable closure means, to prevent foam leakage and escape of shrapnel or noxious gases.

As seen in Figure 2, the enclosure 10 is made of a composite textile material, including a central layer 20 of a ballistic fabric material (one such material is sold under the trademark Dyneema), sandwiched between inner and outer layers 22 of a light-weight rip-stop nylon fabric material. Other useful ballistic materials include Kevlar™ or equivalents. The materials are sewn together in sections. In some embodiments this layer can be eliminated ort several layers of the ballistic fabric material are provided i.e. depending upon the threat to be addressed. Weight is also a consideration. For example, a 2.13m (7 foot) diameter enclosure with three ballistic layers weighs 13.5kg (30 pounds), which is the practical limit for a man dressed in a bulky bomb suit to carry any appreciable distance. A 1.5m (five foot) enclosure with four ballistic layers would also meet this criterion.

In some cases, instead of the extra ballistic layers, a hemispherical fly (not shown) is added as an overlay to enclose the structure. The fly is made of the same multiply textile material as the enclosure. Additional flys can be added, depending on the nature/energy of the explosive device, to ensure containment of the resulting shrapnel. The extra ballistic layers are preferred, since the flys add to setup time and effort.

Figure 3 illustrates an embodiment of the apparatus which employs a flexible external frame 32, which will flex to pass through openings, such as doorways, which are made smaller than its diameter.

In the embodiment shown, the frame 32 includes three semi-circular hoop-like pole members which are disposed in a criss-cross manner and spaced equidistant from each other to form the frame. This arrangement facilitates the positioning of the apparatus without modification, by a robot arm or the like. The poles are made of fibreglass to avoid shrapnel formation, but could be made of other flexible light-weight material or could be integral air tubes.

The enclosure is made of a composite textile material similar to that of the figure 1 embodiment, the difference being that the inner and outer layers are of a waterproof nylon textile material.

The outer layer of the enclosure 10 includes a plurality of tab portions 34 for attachment to the frame 32. Wider tabs 36 are provided adjacent the top for added strength at this location. Although the tabs are formed as loops in the embodiment shown, it will be appreciated that other known attachment means could be used. In this embodiment the enclosure 10, includes six identical triangular panels 13, and an integral hexagonal floor 40 which approximates a circle. Foam injection openings 12 are provided in alternate panels. Closure flaps 15 of the same composite material as the panels are also provided. The flaps are secured e.g. by Velcro® fasteners. The floor 40 includes positioning means in the form of a central opening 42 for positioning an explosive device, substantially equidistant from any point on the enclosure wall. The integral floor ensures that there are no weak spots or corners, which have been known in the prior art to fail.

Also in this embodiment, the door opening 14 is provided in one of the panels, and includes a large zipper closure means to facilitate operation by gloved hands.

Upon filling with foam the enclosure inflates to form a hemispherical shape, with the explosive device positioned substantially equidistant from any point on the enclosure wall. The enclosure wall is rounded adjacent to the floor, having a flattening effect on the enclosure shape. This positioning and rounded enclosure wall provide for optimum distribution of the blast force in all directions toward the enclosure wall, providing for the successful integration of various blast scenarios, as described below.

In fact, the combination of these two features has proven capable of withstanding around twice the explosive force, as compared to the Figure 1 embodiment. See tests #3 and 4.

The method according to the invention comprises placing the enclosure 10 over an improvised explosive device (IED) at 30, and the enclosure is filled with a suitable aqueous energy absorbing, flowable foam material (e.g. Silvex®). See US Patent No. 4,770,794 of 13 September 1988, the disclosure of which is incorporated herein by reference. Useful foams comprise 1-5 %/w of active foam forming ingredients. We have found that a particularly useful foam material of this nature comprises 1 -3%/w of active foam forming ingredients, the balance being water, and has an expansion ratio of 17-49:1. Such foams exhibit good stability and drainage properties and can be used in relatively small amounts as indicated in the Examples which follow. The foam is introduced into the enclosure at a flow rate of 151-3021 (40-80 US gallons) /minute, preferably 141-2261 (40-60 US gallons)/minute though filling port 12, using a standard foam generating fire truck, or a portable pump and foam generating system. The flow rate is expressed as flow rate of water into a foam generator. The flow of foam into the enclosure is actually about 2-3 times faster, because of the larger volume of the foam. When the IED is detonated, none of the resulting IED fragments penetrate the enclosure. Apparently, the lines of force from the explosion are directed radially outwardly from the IED and the force or energy from the blast is absorbed by the surrounding foam. The smooth concave shape of the enclosure which acts as a mold for the foam, and/or the corresponding convex shape of the foam also plays a role, since other configurations tested such as cubes, rectangles and cylinders fail at the comers.

Other inessential features include the following.

The provision of an integral tent floor (figure 3) with a central IED receiving opening would prevent the foam from flowing out around the bottom. Preferably, the fabric surrounding the central opening is made more flexible by the inclusion of an elasticized retainer which forms oversized gores 44. This minimizes blast damage to the floor. In another embodiment (not shown) the floor would be made of a net material.

An internal frame (not shown) or an external exoskeleton (Figure 3) could be included to facilitate erection and maintain the structural integrity of the dome following the explosion. It will be appreciated that the dome can be erected by filling with the foam.

EXAMPLES

For the explosive device tested, not only is the blast suppressed, but the shrapnel from the blast is contained within the structure.

Testing of the Explosive Device Containment System

This Explosive Device Containment system is a 2.13m (7 ft) hemispherical shaped enclosure filled with foam (approx. 0.028m³ (570 cubic feet)). The enclosure is fabricated with a 3 layer textile composite. The outside and inside layers are a light rip-stop nylon and the inside layer is a ballistic product called DYNEEMA®. Depending upon the threat, additional ballistic layers and/or flys are provided, as described above. The foam is generated using an air aspirating foam nozzle (cylindrical, length=25 cm, diameter=15cm) with an expansion ratio of about 25:1 with an operating pressure of about 70 PSI and a flow rate of 215-2271 (57-60 US gallons) of foam solution/minute. The foam concentrate comprises about 1.7%/w Silvex® in water. The nozzle is the subject of our co-pending US application, Serial No. 08/758,075, filed 27 November 1996.

Test Objective:

To establish the explosive blast and explosive fragment mitigation qualities of the Explosive Device Containment System.

Test #s 1 and 2 were done with the Figure 1,2 embodiment, and tests #s 3 and 4 with the Figure 3 embodiment. Also, in test #3, the composite included five ballistic layers. In test #4, two additional flys were included.

Test #1 Explosive Device:

Pipe bomb constructed of a 30cm x 6cm (12"x21/2") diameter steel pipe with end caps threaded on both ends containing approximately 0.68kg (1.51bs) of dynamite initiated by a standard electric blasting cap. The multi layer composite, plus two additional flys, is used in this test.

Results:

After the pipe bomb was functioned none of the pipe fragments were found to have penetrated the enclosure. This was very significant as it confirmed this technique was effective in containing a very energetic explosive device, the fragments form the type of explosive device can be projected at velocities in the order of 1524-2134m (5000-7000 feet)/sec. and up to 183-274m (200 to 300 yards).

Test #2: Explosive Device:

Steel tool box approx. 45.7cmx25.4cmx20.3cm (approx. 18"x10"x8") containing 1kg (2.21bs) of C-4 explosive initiated by a 0.09kg (.2 lbs) Initiation charge. The five layer composite is used in this test.

Results:

After the device was functioned an examination of the enclosure revealed that all fragmentation from this device was contained in the system. This is quite significant as it confirms that this system is very effective in neutralizing the very energetic effects of large and destructive explosive devices.

Test #3 Explosive Device:

Pipe bomb constructed of a 30cmx6cm (12"x21/2") diameter steel pipe with end caps threaded on both ends containing approximately 0.68kg (1.51bs) of dynamite initiated by a standard electric blasting cap. The multi layer composite, plus two additional flys, is used in this test.

Results:

After the pipe bomb was functioned none of the pipe fragments were found to have penetrated the enclosure. This was very significant as it confirmed this technique was effective in containing a very energetic explosive device, the fragments form the type of explosive device can be projected at velocities in the order of 1524-2134m (5000-7000 feet) /sec. and up to 183-274m (200 to 300 yards) .

Test #4: Explosive Device:

Steel tool box approx 45.7cmx25.4cmx20.3cm (approx. 18"x10"x8") containing 1kg (2.21b) of C-4 explosive initiated by a 0.09kg (.21bs) initiation charge. A five layer composite is used in this test.

Results:

After the device was functioned an examination of the enclosure revealed that all fragmentation form this device was contained in the system. This is quite significant as it confirms that this system is very effective in neutralizing the very energetic effects of large and destructive explosive devices.

General Comments:

Both these devices represent examples of very energetic explosive devices. These devices can result in the projection of high velocity fragments causing considerable injuries and property damage. This system could be used by both police and military Explosive Ordnance Units. It is a portable system that can be positioned in a very short time.
Although Silvex has been used to illustrate the operation of our invention, it will be appreciated by those skilled in the art that many other foam materials may also be used, including those containing biological/chemical decontaminating agents, provided that they are formulated to exhibit the requisite expansion ratio and other related properties discussed above.

Claims

An apparatus for suppression of a blast from an explosive device, comprising

a) a hemispherical enclosure (10) defined by an upstanding wall, wherein the enclosure is made of a composite textile material, comprising one or more layers (20) of a ballistic fabric material, sandwiched between inner and outer layers (22) of a light-weight rip-stop nylon fabric material,

b) positioning means (42) associated with the enclosure for positioning the explosive device within the enclosure substantially equidistant from any point on the wall,

c) an opening (14) in the wall, and

d) an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, substantially filling the enclosure and covering the explosive device, whereby upon detonation of the explosive device so positioned, the blast is suppressed.
Apparatus according to claim 1, wherein the enclosure (10) is inflatable.
Apparatus according to claim 2, whereby upon filling the enclosure is inflated by the foam.
An apparatus according to claim 2 or claim 3, wherein upon inflation the enclosure (10) is rounded adjacent to the integral floor.
Apparatus according to any of the preceding claims, wherein the enclosure includes an integral floor, and wherein the positioning means comprises a central opening (42) in the floor.
An apparatus for suppression of a blast from an explosive device, comprising

a) a hemispherical enclosure (10) defined by an upstanding wall, wherein the enclosure includes an integral floor, and wherein the enclosure is inflatable and wherein upon inflation the enclosure wall is rounded adjacent to the integral floor,

b) positioning means associated with the enclosure for positioning the explosive device within the enclosure substantially equidistant from any point on the wall, the positioning means comprising a central opening (42) in the floor,

c) an opening (14) in the wall, and

d) an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, substantially filling the enclosure and covering the explosive device, whereby upon detonation of the explosive device so positioned, the blast is suppressed.
Apparatus according to any of the preceding claims, wherein the diameter of the enclosure (10) is about 1.5-2.7m (5-9 feet).
Apparatus according to any of the preceding claims, wherein the volume of the enclosure (10) is about 0.028m³ (570 ft³).
Apparatus according to any of the preceding claims, wherein the foam material comprises 1-5 % w/v of active foam forming ingredients, the balance being water.
Apparatus according to any of claims 1 to 8, wherein the foam material comprises 1.7 % w/v of active foam forming ingredients, the balance being water.
Apparatus according to any of the preceding claims, wherein the expansion ratio of the foam material is about 25:1.
An apparatus according to any of the preceding claims, further comprising a flexible frame (32) to support the enclosure during positioning and use.
A method for suppression of a blast from an explosive device, comprising

a) providing a hemispherical enclosure (10) defined by an upstanding wall, wherein the enclosure is made of a composite textile material comprising one or more layers (20) of a ballistic fabric material, sandwiched between outer and inner layers (22) of a waterproof nylon fabric material,

b) positioning the explosive device within the enclosure, substantially equidistant from any point on the wall, and

c) substantially filling the enclosure and covering the device with an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, whereby upon detonation of the device so positioned, the blast is suppressed.
A method according to claim 13, wherein the enclosure (10) is inflatable.
A method according to claim 14, whereby upon filling the enclosure is inflated with the foam.
A method according to claim 14 or claim 15, wherein upon inflation the enclosure wall is rounded adjacent to the integral floor.
A method according to any of claims 13 to 16, wherein the enclosure (10) includes an integral floor with a central opening (42), and wherein the explosive device is positioned in said opening.
A method for suppression of a blast from an explosive device, comprising

a) providing a hemispherical enclosure (10) defined by an upstanding wall, wherein the enclosure includes an integral floor with a central opening (42),

b) positioning the explosive device in said opening (42) within the enclosure, substantially equidistant from any point on the wall, wherein the enclosure is inflatable, and upon inflation the enclosure wall is rounded adjacent to the integral floor, and

c) substantially filling the enclosure and covering the device with an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, whereby upon detonation of the device so positioned, the blast is suppressed.
A method according to any of claims 13 to 18, wherein the foam material comprises 1-5 % w/v of active foam forming ingredients, the balance being water.
A method according to any of claims 13 to 18, wherein the foam material comprises about 1.7 % w/v of active foam forming ingredients, the balance being water.
A method according to any of claims 13 to 20, wherein the expansion ratio of the foam material is about 25:1.